Israel's former Prime Minister Shimon Peres called for the international community to shun Iran.

He said: "Iran is the only member of the United Nations that threatens publicly to destroy another member of the United Nations. It is a call for genocide."

The Israeli leadership had already become increasingly concerned by intelligence reports on Iran's nuclear project.

Israel is not going to wait until the first nuclear bomb is going to be dropped on Israel

Avi Dichter, Israeli Minister for Public Security

But now Israeli feelings about Iran have reached a critical point. In order to understand Israeli attitudes, it is necessary to get inside the Israeli mindset, to uncover why Iran is being seen as an 'existential' threat - that is, a danger to the nation's very existence.

Why is Israel's fear of attack so intense? And what kind of response could such feelings trigger?

To some in Israel's political world, the country's life is on the line and if some action is not taken, the country could disappear from history in the way that President Ahmadinejad spoke of.

Despite Iran's frequent diplomatic reminders that its nuclear objectives are entirely peaceful, there is a sense of foreboding inside Israel.

The former Prime Minister Ehud Barak sums up his own feelings by drawing on a personal experience after the Yom Kippur war in 1973, when he returned from Israel to live in America.

He said he realised - while watching a football game - that if Israel had lost the war, it would have become a part of history and not a single game of football would be cancelled.

"And I carried this memory with me to the chair of the prime minister. Ultimately we are standing alone."

Nuclear deterrent

According to the respected Carnegie Institute, Israel has its own deterrent, in the shape of an arsenal of as many as 200 atomic warheads.

Iran's heavy water plant at Arak has provoked international criticism

But Israel has never openly acknowledged its atomic programme, and has always maintained that it will not be the first to introduce nuclear weapons in to the Middle East.

The possibility that Iran could build nuclear weapons is regarded by some of Israel's military and political class as an unacceptable danger, putting the world's most dangerous weapons in the hands of their enemies.

The former head of Israel's security service Shin Beit, Avi Dichter, believes Israel must now adopt a "preventative" approach.

"I was an Air Marshal and I was trained to open fire towards a terrorist once I identified two things: one that he has a means of warfare, a pistol, a hand grenade, etc, and the second that he has an intention to use it in order to kill innocent people," says Mr Dichter, who is now Israel's minister for Public Security.

"Israel is not going to wait until the first nuclear bomb is going to be dropped on Israel."

Western intelligence services claim they have good evidence that Iran is developing atomic weapons and President Bush has declared that he will not permit a nuclear armed Iran.

But with its ongoing commitments in Iraq, some of Israel's strategic thinkers believe America has too much at stake to intervene militarily.

Iraq precedent?

Meanwhile, Israel's foreign minister has said publicly that time is running out. This scenario begs the question: could Israel act against Iran on its own?

Twenty five years ago, it did precisely that. The Iraqi nuclear reactor at Osirak was potentially capable of producing material for atomic weapons.

America was then backing Saddam Hussein's regime, and seemed unlikely to take hostile action against a nation at war with Iran.

In 1981, when the reactor was nearly complete, Prime Minister Begin of Israel felt that the threat required immediate action. He decided to go it alone and launch a raid to destroy the nuclear plant. Eight Israeli F-16 fighters bombed the Iraqi facility, in what was seen in Israel as a model of pre-emptive action.

As a last resort, the West should be ready to launch military strikes to deal with Iranian nuclear capabilities.

Moshe Yaalon, former chief of staff, Israeli armed forces

Could this happen again? According to Israeli intelligence sources, Iran's scientists are now within a year of reaching the technical point when they could enrich uranium to the level required for atomic arms.

This is regarded in Israel as the point of no return, after which Iran would allegedly be able to produce the uranium needed at secret sites.

Some Israelis think this is the moment when action should be taken. For them, a nuclear armed Iran is a doomsday scenario.

Israel's war with Hezbollah this summer reminded Israelis of Iran's reach beyond its own borders. Iran is widely believed to provide support and weaponry to Hezbollah.

The end of the conflict left Israel's government and its military under investigation for what was seen as a failure to defeat the Islamic militant movement convincingly.

Some inside Israel believe that Israel must turn its attention directly to Iran.

The former chief of staff of Israel's armed forces, Moshe Yaalon concludes: "As a last resort, the West should be ready to launch military strikes to deal with Iranian nuclear capabilities ...but Israel should be ready to deal with this kind of threat, if anyone else doesn't do it."

Will Israel bomb Iran? was broadcast on Tuesday, 10 October, 2006 at 21.50 BST on BBC Two